Process of purifying fatty acid derivatives of mineral oil



' I Octr24, 1933. ALLEMAN 1,931,855

PROCESS OF PURIFYING FATTY ACID DERIVATIVES OF MINERAL OIL Filed Nov. 5, 193 0 fllcoiol afia'fdj/ 4706;15

Sieflfoz Mm): M/VENI'OR ll/a voratcon/ WITNESS: 7 w KjuxhuA/ Patented Oct. 24, 1933 PROCESS OF PURIFYING FATTY ACID DE- RIVATIVES OF MINERAL OIL Gellert Alleman, Wallingford, Pa, assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application November 3, 1930. Serial No. 493,052 8 Claims. (01. 260-1167 Soaps and organic or fatty acids derivable from petroleum are of great commercial value and are used in the manufacture of cutting oils and'have a wide variety of other useful applica- 5 tions. The main, if not the only, known source for these materials has been the precipitate produced in the alkali treatment of acid-treated mineral oil lubricating stock. However, in the most advanced processes of distilling lubricating oil (see the Pew Patent 1,761,153, June 3, 1930), the lubricating oil distillates require no acid and alkali treatment and the .soda sludge is not produced, thereby eliminating the source from which these valuable soaps have hitherto been produced.

It has been discovered, however, that the asphaltic still bottoms which are produced in the manufacture of lubricating oil in accordance with the process of said Pew process contain sodium salts of certain organic acids which are reaction prodo ucts incidental to the distillation process in the presence of sodium hydroxide, and the discoverer I has succeeded in separating this'material from the residual asphalt with the resultant production, the resultant products being a high grade ,5 commercial insoluble-in-water asphalt :and a soap-water solution .or dispersion which may be acidified with mineral acid to yield water-insoluble organic acids. The latter material also contains hydrocarbons and resinous substances, is of a light chocolate color and holds entrained with it about of water. washed with'hot water until the final washings no longer react to litmus or methyl orange.

One method of extracting this material from ;5 the residual asphalt from the lubricating oil still is fully setforth in an application filed by Harry Angstadt November 3, 193e, Serial No. 493,242 but my invention is not dependent upon any particular process for extracting these so-called fatty ,0 acids'from the residual asphalt. It is believed,- however, that in any process for extraction of these acids they will necessarily containa considerable proportion of colored hydrocarbons and petroleum resins and will hold entrained a large .5 proportion of water. For most, if not all, com- 7 mercial purposes, these fatty acids require dehydration and the removal therefrom of avsubstantial proportion of the colored hydrocarbons and also, preferably, a substantial proportion of the i0 petroleum resins. It is the obj ect of this invention to effect the desired purification of these fatty acids to adapt them to all commercial uses.

In one procedure for extracting the mass of fatty acids, colored hydrocarbons and petroleum V saponifled with sodiumhydroxide or other sult- 110 i5 resins, the water, which, as above stated, is pres- It may be repeatedly ent in the proportion of approximately fifty per cent., can be removed byheat, but a temperature of about 170 C. must be reached before all of the water present is removed, and at this temperature, in the presence of air, considerable decompostion takes place. Ihave found that the water can be removed and the acids and accompanying hydrocarbons and resinous materials rendered anhydrous by adding commercial xylene to the fatty acid-hydrocarbon-resinous mass, and distilling off the xylene. Commercial xylene, which boils between approximately 135 C. and 145 C., forms a minimum boiling point 'ure with water, which resultant mixture boils at about 94 C. When the m'mture is heated, xylene and water distil over at about 94 C. and the water separates, at the bottom, from the distillate. The separated xylene is used over again and there is practically no loss in its employment, Under these conditions the fatty acid-hydrocarbon resinous mass is rendered anhydrous and has an average acid number of about 50. It is known that a mixture of about 91 per cent. benzene and 9 per cent. water boils at 69 C.; that a certain mixture of toluene and water boils at about 84 0.; and that certain'mlxtures of water and normal propyl alcohol, water and isopropyl alcohol, water and butyl alcohol, water and isobutyl alcohol, water and secondary butyl alcohol, water and tertiary butyl alcohol, water and isoamyl alcohol, and water and tertiary amyl alcohol, boil at temperatures" below the boiling point of water or below the boiling point of the specific component mixed witll water. v I have determined that solvent naphtha, which is derived from the light distillates of coal tar, can also be used in this connection.

I prefer, however, to employ industrial xylene on account of its better adaptability insofar as efficiency and the ease of its recovery are concerned and also because of its availability and its reasonable cost.

In claiming distillation of the water with xylene, it will be understood that I mean to include as equivalents of the latter any substance, such as those mentioned, having the specified characteristics of xylene, that is, which, mixed with water, has a boiling point below that of water or below the point of the fattyacid-colored hydrocarbon-resin mass mixed. with water. 4

The anhydrous fatty aeid-hydrocarbon-resinous material resulting from the described distillation with xylene, when dissolved-in oil and obtained, but at least so per cent. of the material was decomposed in the distilling process. Distillation niay be resorted to, however, if commercial needs, in any given case, are satisfied by the production of fatty acids of high acid number at the expense of substantial loss of fatty acids by decomposition. 4

I have found it practicable, however, to recover practically all the fatty acids substantially free from the colored hydrocarbons or resinous materials by a chemical process of selective solubility. I have determined that anhydrous methanol and anhydrous ethanol as well as certain other alcohols will dissolve the anhydrous fatty acids and will not dissolve the colored hydrocarbon-resinous mass, at least to any appreciable extent. The choice of a solvent is of great importance. The most desirable solvent (or combination of solvents) is one which dissolves the maximum amount of the fatty acids and the minimum amount of the objectionable colored hydrocarbons and pertoleum resins. The boiling point of the solvent is also of importance. It must not be so readily volatile that when the sticky, viscous mass of fatty acid-colored hydrocarbons-petroleum resins is heated to reduce its viscosity in order that the mass can bestirred, the solvent will boil. The boiling point of the solvent must not be too high (say 180 C.) otherwise a portion of the fatty acids will decompose during the recovery of the solvents and the desired product will have an objectionable color due to the decomposition products. Among the more desirable solvents, I would specify: anhydrous methanol, anhydrous ethanol, anhydrous isopropanol, anhydrous tertiary bntanol, anhydrous tertiary amyl alcohol, anhydrous denatured ethanol containing about one per cent, aviation gasoline, and anhydrous denatured ethanol containing about ten per cent. methanol.

Methanol, in consequence of its lower boiling point, is not as desirable as ethanol, for the reason that the sticky mass must be heated in order to keep'it liquid and sometimes it is necessary to heat it to about the boiling point of methanol.

' It is important. that the solvent used shall be absolute, i. e., free from water; After a great "number of experimental have concluded that anhydrous ethanol; or anhydrous denatured ethanol containing one per cent. aviation gasoline,

percent. methanol, are among the best solvents which dissolve a maximum amount of the fatty ratus in vertical section. m

vessels A and 3.

This apparatus comprises two upright or pref erably spherical vessels, both of which are arranged for the application of external heat. The bottom of one, the upper vessel, A, is on a level with the top of the other, or lower vessel, B, in order to permit gravity drainage; and, for convenience, has a capacity slightly less than the lower vessel. Vessel A is provided with: (l) a mechanical stirrer D, the shaft of which passes through a mercury seal, or packing gland H; .(2) a tube E, extending to the upper surface of the tarry material and connected to the trap G under. the condensers I for the delivery of the hot (but not boiling) alcohol; (3) a constant overflow tube F for the delivery of the alcoholic solution of the fatty acids to vessel B through trap C, which latter retains any colored sludge or asphalt which, in consequence of too violent agitation or stirring, may have passed through the overflow. If the stirring is properly regulated, the heavier materials remain in the bottom of vessel A and only the alcoholic extract of the acids passes through the overflow tube.

Vessel B is a still from which the alcohol is distilled and to which the alcoholic solution of the fatty acids is returned bygra-vity how, the alcohol being distilled repeatedly and entering vessel A for continuous extraction. Below the condensers is a receptacle or rap G so arranged that hot alcohol is delivered to vessel A, the heat from the vapors of alcohol passing through this condensed liquid keeping it almost at its boiling point. llhe overflow from vessel A passes through the tube F to the trap C, the tube entering from the top and extending to the bottom. From this trap the alcoholic extract flows from an outlet near the top to vessel 3 This arrangement traps any heavy, colored resinous or hydrocarbon material (which in consequence or the violent stirring may have passed through the overflow tube), which material-settles to the bottom and is withdrawn when necessary through the bottom outlet K. In case it is desirable to stir more rapidly in order to hasten the extracin'on, two or more traps may be installed between vessel A and vessel B. It is important to have certain connecting pipes partly-cut away on both sides and glass tubes inserted so that the charactor of the liquids passing through may be observed. smal port holes fitted with glass plates are convenient for observing what takes place in The extraction operation is carried out as follows: Vessel A is filled about one-half full with the fatty acid-colored hydrocarbon-resinous mass and the remaining lialf with the anhydrous solvent. Vessel B is half filled with the anhydrous solvent. Vessel A is externally heated,

or anhydrous denatured ethanol containing 10" but not to the boning mint of the solvent sel Bis externally heated so that the solventboils. is condensed, passes, heated almost to its boiling point, 'to trap ,G, and then overflows by gravity to the massbelng extracted. 'Ihestirrer is operated at sucli a rate or speed as to prevent too violent agitation of the heavy mass at the bottom, thus preventing it from reaching the outlet overflow tube.

After the extraction has been completed the alcoholic extract is transferred to another vessel and the alcohol recovered by distillation.

Instead or transferring the alcoholic extract from vessel B to another distilling vessel, it may be distilled from vessel B, but it is preferable to 'malgethe transfer in order to remove any parrev Ill!) ticles of .tar or sludge which, due to too violent stirring, may have passed over.

In another procedure for the intermittent extraction of themass of fatty acids, colored hydrocarbons and petroleum resins, in order to obtain relatively pure fatty acids, the mass, after removal of the water contained in it, is placed in an upright closed .tank (preferably provided with a conical bottom) and there is added thereto about three times its volume of one of the preferred solvents hereinbefore specified, the whole being heated under pressure to about 120 C. Apparently the whole mess is quickly dissolved or dispersed in the solvent. Upon cooling, most of the colored hydrocarbons and petroleum resins settle to the bottom andmay be withdrawn, but it is preferred to remove the solution of fatty acids by siphoning off from the top. The solvent is then recovered by distillation. The fatty acids remaining in the still are removed therefrom, dissolved in oil and saponified with caustic soda or other appropriate alkali. This saponified product, when mixed with water, forms a stable emulsion.

The fatty acids obtained by either of the described procedures have, in general, the characteristics of those specified in my Patents Nos.

1,694,461 and 1,694,463. They have an acid num-' ber ranging from 85 to 125. The extracted material evidently contains varying amounts of non-colored hydrocarbons or other non-acid materials, but the presence. of the latter is not objectionable because they do not add color to the soaps which are made from these fatty acids. Vvhen dissolved in lubricating oil and saponified with caustic soda (orother suitable alkali), they ing the recovery of the solvent, and which may be removed from the extract by distillation or otherwise-so as to separate out a relatively high acid number and not objectionable colored fatty acid.

In extracting these fatty acids with methanol,

ethanol, and other alcohols, as above described,

an appreciable amount of esters (or ethereal salts) of these fatty acids is formed. The amount of such formation depends upon the temperature to which the mass is heated during the extraction process and the timeduring which the alcoholis in contact with thefmassto be extracted. If the temperature is relatively high and the extraction takes place over a long period of time, more esters are formed than when .the extraction is carriedout at a lower temperature and in a shorter time. The quantity of esters sometimes amounts to as much as about percent.

I The presence of these esters in the extracted fatty acids is not objectionable, as they are -readily soluble in oil and are saponifiable upon the addition of caustic soda orother suitable alkali. When dissolved in Oil and'saponifled,

\ they yield permanentemulsions when placed in water.

which comprises adding to themass xylene to form with the water. a mixture having a. comparatively low boiling point and distilling off the xylene andwate-r, thereby yielding as a residue anhydrous partially purified fatty acids which, when dissolved in oil and saponified with an alkali hydroxide, form with water a substantially permanent emulsion.

3. The process of treating a mixture: contain-" ing water, soaps and colored hydrocarbons extractedfrom the asphalticresidue of mineral oil stills, to recover fatty acids of high acid number devoid of objectionable color, which comprises separating the asphalt from a mass containing water, soaps and colored hydrocarbons, acidifying, adding xylene, distilling-off xylene and water, and extracting the fatty acids with anhydrous ethanol.

4. The-process of treating a mixture containing asphaltic material, petroleum soaps and colored hydrocarbons and having the character'- istics of residues of asphalt base petroleum oils, to recover fatty acids of high acid number devoid of objectionable color, which comprises'separating the asphalt from a mass containing water,

soaps and colored hydrocarbons, acidifying, add- 1 ing xylene, distilling ofi the xylene and water, separating the xylene from the water and reusing it as specified, extracting the anhydrous fatty acid colored hydrocarbon mass with anhydrous ethanol, recovering the fatty acids by distilling the ethanol, and re-using the ethanol as specified.

- 5. The process of treating a mixture containing asphaltic material, petroleum soaps and colored hydrocarbons and having the characteristics of residues of asphalt base petroleum oils, to recover fatty acids of high acid number devoid of objectionable color, which comprises separating the asphalt from a mass containing water, soaps and colored hydrocarbons, acidifying, adding xylene, distilling off the xylene and water, vaporizing anhydrous ethanol, condensing the anhydrous ethanol and subjecting a mixture I thereof with the fatty acids to a temperature belowbut approaching the boiling point of the ethanol, continuously removing the alcoholic extract of fatty acids, and distilling oil the ethanoL' 6., The process of treating a mixture containing asphaltic material, petroleum soaps and colored hydrocarbons and having the character-y istics of residues of asphalt-base petroleumfoils, to recover fatty acids of high acid number devoid of objectionable color, which comprises separating the asphalt from a mass' containing water, soaps and colored hydrocarbons, acidiethanol, continuously removing the alcoholic extract of fatty acids, trapp the alcoholic solu tion to separate out colored llvolroeexloom material, and olistg ofi the ethanol.

7. The processof treating 9. mixture eontolim= ing aspheltlc materiel, petroleum meme, metro leum soaps soluble in petroleum and coloreol hydrocarbons leaving the ellereeterlstlcs oil vresidues of asphalt hose petroleum oils, to re= memes) lemme veslmo and} colored lzyelroceelaone will sep= from the fotty eolcls, and ollstl oil the solvent from the pertlelly purified fatty eeifle.

ll. Toe pmeeso of treating a, water solution of eozliom seeps of fatty acids derived 56mm the espheltle residuum of mineral oll wool eontolm log eleo colored hydrocarbons and petmleum which comprises acidifying the seeps, ooldlng Ecwiol :wlene and distilling 0% the xylene and woter o temperature below the boiling point of water, tloerelov yielding as o residue on zmloy= clroos ooltlelly purified fatty ocld--lnyolroeex= boo-resinous mess fee-e of xylene eml which, if cllseolveol m oll one; slammed with on ollzoll ltyolrosdde, forms with water 22; smbstentlollv permzment emulelol'l.

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